Dear Ethayathulla ,
did you solve the structure by SeMet MAD or some other way?
Sometimes you get strange densities around the ends of methionine side
chains (around the S/Se) when switching from SeMet data to native.
Cheers
Ed
______________
T.Edwards Ph.D.
Astbury Centre for Structural Molecular Biology
University of Leeds, Leeds, LS2 9JT
Telephone: 0113 343 3031
-----Original Message-----
From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On
Behalf Of Ethayathulla Abdulsamath
Sent: Fri 13 Apr 2007 10:51
To: [EMAIL PROTECTED]
Subject: [ccp4bb] Unusual Difference Fourier near Methionines
Dear all
I am doing one structure at 2.6A resolution where I found
unusual density near methionines. Actually three methionines come close
together nearby and I get difference even at 5sigma cutoff. I don't
understand nature of the density. The amino acid sequnce is same I mean
met by chemical sequncing so there is no change amino acid residues. I
am sending the snapshot of the difference fourier observed at
methionines. The crystal belong to R32 system with one molecule and
biological trimer. In snapshot two of the methionines are symmetry
related.
Details of the data collection.
Data collected at synchrotron
Overall Rsym = 6 % and I/sigma = 2.1. Completeness = 99%
Can anyone suggestion what could be chemical nature for the
difference fourier.
Thanks in advance
Ethayathulla
###################################################
A.S.Ethayathulla,Ph.D.
Department of Biophysics
All India Institute of Medical Sciences
Ansari Nagar
New Delhi-110029
India.
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